soil. 97 



of weight calculated. These experiments will partly account 

 for the high value of soils composed of humus, sand and clay 

 in right proportion. 



The experiment may be varied by using two samples of the 

 same clay soil of equal weight and with equal quantities of 

 water added, one being mellow the other pressed. This will 

 show the greater retaining power of mellow over packed or 

 sun-baked clay. 



Field observations should be assigned when studying the 

 important phenomena of water capacity of soils. 



Other ways of determining the soil's capacity for retaining 

 moisture may be proposed. Encourage pupils to suggest 

 experiments ; indeed it may sometimes be advisable to adopt 

 an inferior method devised by the pupils than a superior 

 one that you had thought of yourself. Propose yours 

 and have both compared ; try both methods. Here are 

 a half-dozen samples of soil. After they are dried and 

 crumbled weigh out a half-pound of each to be put in similar 

 funnels, or lamp chimneys, or inverted ink bottles or tumblers 

 or gem jars. Add to each a pint or smaller definite quantity 

 of water and catch and measure the drainage. The less the 

 drainage the greater the retaining power of the soil. If lamp 

 chimneys or tumblers are used the ends or mouths must 

 have cheese cloth tied over them ; if ink bottles, the bottoms 

 may be cracked off with a red-hot iron. All should have a 

 fine wire screen or cheese cloth below the soil to hold it 

 from coming out. 



Capillarity of Soil. — In some situations the subsoil serves 

 like a floor to hold water, and the tilled soil draws it up to 

 feed the roots of plants. This power of drawing up water is 



